Showing papers on "Welding published in 2008"
TL;DR: In this article, the authors deal with the fundamental understanding of the process and its metallurgical consequences, focusing on heat generation, heat transfer and plastic flow during welding, elements of tool design, understanding defect formation and the structure and properties of the welded materials.
1,811 citations
25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an attempt has been made to understand the mechanism of friction stir weld formation and the role of the friction stir welding tool in it by understanding the material flow pattern in the weld produced in a special experiment.
Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.
418 citations
TL;DR: A comprehensive literature review of the application of evolutionary algorithms, evolutionary algorithms and computational network in the area of welding has been introduced herein and was classified according to the output features of the welding, i.e. bead geometry and mechanical properties of the welds.
411 citations
TL;DR: In this paper, the effect of tool pin profile and tool shoulder diameter on FSP zone formation in AA6061 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the FSP zones formation.
404 citations
TL;DR: In this article, the effect of welding speed and tool pin profile on FSP zone formation in AA2219 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the formation.
318 citations
15 Jan 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effects of tool rotational speed and welding speed on the microstructure and tensile properties of Mg alloy have been evaluated, and the effect of the welding speed has been shown to have a significant effect on the Mg microstructural properties.
Abstract: The microstructural change in AZ31B-H24 magnesium (Mg) alloy after friction stir welding (FSW) was examined. The effects of tool rotational speed and welding speed on the microstructure and tensile properties were evaluated. The grain size was observed to increase after FSW, resulting in a drop of microhardness across the welded region from about 70 HV in the base metal to about 50 HV at the center of the stir zone. The obtained Hall–Petch type relationship showed a strong grain size dependence of the hardness. The aspect ratio and fractal dimension of the grains decreased towards the center of the stir zone. The welding speed had a significant effect on the microstructure, with larger grains at a lower welding speed. The yield strength and ultimate tensile strength increased with increasing welding speed due to a lower heat input. A lower rotational speed of 500 rpm led to higher yield strength than a higher rotational speed of 1000 rpm. The friction stir welded joints were observed to fail mostly at the boundary between the weld nugget and thermomechanically affected zone at the advancing side. Fracture surfaces showed a mixture of cleavage-like and dimple-like characteristics.
317 citations
TL;DR: In this paper, a three-dimensional, thermo-elastic-plastic, large deformation finite element method (FEM) is used to simulate welding distortion in a low carbon steel butt-welded joint with 1mm thickness.
315 citations
TL;DR: In this paper, the basic elements of the thermal modelling of friction stir welding are presented and some results from a new thermal pseudomechanical model in which the temperature-dependent yield stress of the weld material controls the heat generation are also presented.
277 citations
TL;DR: In this article, the effect of process parameters such as tool rotational speed, traverse speed and axial force on tensile strength of friction stir welded RDE-40 aluminium alloy was evaluated.
245 citations
TL;DR: In this paper, the microstructural and mechanical properties of the friction stir welding (FSW) of 1060 aluminum alloy to a commercially pure copper were investigated. And the effect of formation of hard and brittle intermetallic phase at the interface of the joints on the shear strength of the joint was discussed.
243 citations
TL;DR: In this article, the effect of axial force and tool pin profiles on FSP zone formation in AA6061 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the formation.
Abstract: AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to the fusion welding processes that are routinely used for joining structural aluminium alloys, the friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force etc., and the tool pin profile plays a major role in deciding the weld quality. In this investigation an attempt has been made to understand the effect of axial force and tool pin profiles on FSP zone formation in AA6061 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different axial force levels. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square tool pin profile produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles.
TL;DR: In this paper, Mg-Al-Zn alloys were lap joined using friction stir welding during which the probe of a tool did not contact the surface of the lower Mg−Al−Zn alloy sheet, and micro X-ray diffraction was used to analyze phase transition in the joint.
TL;DR: The AS/NZS 4600 standard is based on the North American Specification published in 2001 with a 2004 Supplement but with special rules for high strength steels as produced in Australia including rules for distortional buckling and welding of high strength steel as mentioned in this paper.
Abstract: The paper describes the new developments in the Australian/New Zealand standard AS/NZS 4600. The developments are based mainly on research in Australia and the USA. They include new rules for high strength steel, the new Direct Strength Method of design as an alternative to the Effective Width Method and many other detailed changes including design of unstiffened compression elements under stress gradient. The standard is based mainly on the North American Specification published in 2001 with a 2004 Supplement but with special rules for high strength steels as produced in Australia including rules for distortional buckling and welding of high strength steel.
25 Nov 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of the welding speed on the microstructure and mechanical properties of the stir zone (SZ) in friction stir welding (FSW) of SAF 2205 duplex stainless steel was investigated.
Abstract: The present study focuses on the effect of the welding speed on the microstructure and mechanical properties of the stir zone (SZ) in friction stir welding (FSW) of SAF 2205 duplex stainless steel. A single tool, made of a WC-base material, was used to weld 2 mm-thick plates at a constant rotational speed of 600 rpm. X-ray radiography revealed that sound welds were successfully obtained for the welding speeds in the range of 50–200 mm/min, whereas a groove-like defect was formed at the higher speed of 250 mm/min. Moreover, increasing the welding speed decreased the size of the α and γ grains in the SZ, and hence, improved the mean hardness value and the tensile strength of the SZ. These results are interpreted with respect to interplay between the welding speed and the peak temperature in FSW.
TL;DR: In this article, the effects of welding speed and fixed location of base metals on microstructures, hardness distributions, and tensile properties of the welded joints were investigated, and the maximum tensile strength was achieved for the joint produced at welding speed of 1.67 mm/s when 2024 Al alloy was located on the advancing side.
Abstract: The present study focuses on the microstructure and mechanical properties of dissimilar joints of 2024-T3 Al alloy to 7075-T6 Al alloy produced by friction stir welding. Effects of welding speed and fixed location of base metals on microstructures, hardness distributions, and tensile properties of the welded joints were investigated. SEM-EDS analysis revealed that the stir zone contains a mixed structure and onion ring pattern with a periodic change of grain size as well as a heterogeneous distribution of alloying elements. The maximum tensile strength of 423.0 MPa was achieved for the joint produced at welding speed of 1.67 mm/s when 2024 Al alloy was located on the advancing side.
TL;DR: In this article, a new complex Fe-Cr-W-Mo-Nb alloy with high boron content was set into comparison with lower alloyed materials on basis Fe−Cr-B-C, a synthetic multiphase alloy on iron base with around 50.1% tungsten carbides and a crack free martensitic Fe•Cr-C alloy containing finely precipitated Niobium carbides.
TL;DR: In this paper, the authors discussed the nature of residual stresses in welded structures in terms of their magnitude, directionality, spatial distribution, range and variability, and the effects of the following factors on the residual stresses: material properties, material manufacture, structural geometry, fabrication procedure, welding procedure, post-weld treatments and service conditions.
TL;DR: In this paper, a CO 2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless-steel and low carbon steel plates with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile.
Abstract: In the present work, CO 2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless-steel and AISI 1009 low carbon steel plates. Laser power, welding speed and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless-steel with ferritic low carbon steel were evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical design of experiment (DOE) technique for optimizing the selected welding parameters in terms of minimizing the fusion zone. Mathematical models were developed to describe the influence of the selected parameters on the fusion zone area and shape, to predict its value within the limits of the variables being studied. The result indicates that the developed models can predict the responses satisfactorily.
TL;DR: In this paper, a tool for welding was rotated at speeds ranging from 800 to 1600rpm under a constant traverse speed of 300mm/min, and defect free welds were successfully obtained and the surface morphology of the welds became smoother as the tool rotation speed was increased.
TL;DR: In this paper, the effect of processing parameters on mechanical and microstructural properties of AA6082 joints produced by friction stir welding was analyzed by means of tensile tests at room temperature.
TL;DR: In this article, a thermal model of friction stir welding was developed that utilizes a new slip factor based on the energy per unit length of weld, which is derived from an empirical linear relationship observed between the ratio of the maximum welding temperature to the solidus temperature and the welding energy.
Abstract: A thermal model of friction stir welding was developed that utilizes a new slip factor based on the energy per unit length of weld. The slip factor is derived from an empirical, linear relationship observed between the ratio of the maximum welding temperature to the solidus temperature and the welding energy. The thermal model successfully predicts the maximum welding temperature over a wide range of energy levels but under predicts the temperature for low energy levels for which heat from plastic deformation dominates. The thermal model supports the hypothesis that the relationship between the temperature ratio and energy level is characteristic of aluminum alloys that share similar thermal diffusivities. The thermal model can be used to generate characteristic temperature curves from which the maximum welding temperature in an alloy may be estimated if the thermal diffusivity, welding parameters and tool geometry are known.
15 May 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied and it was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side.
Abstract: Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode.
TL;DR: The flow of material around the welding tool during friction stir welding (FSW) is closely linked to many of the key issues related to the process and understanding of the flow is critical to determination of accurate thermomechanical processing conditions during FSW.
15 May 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, an attempt has been made to establish relationship between the base material properties and FSW process parameters such as tool rotational speed, welding speed, axial force, etc.
Abstract: Friction stir welding (FSW) is a solid state welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds.
TL;DR: In this paper, the microstructure and property relationship in aluminum-HSLA steel and aluminum-dual phase steel bimetals fabricated by explosive welding technique was investigated, and it was shown that the plastic deformation of dual-phase steel was higher than HSLA steel near interfaces of bometals.
TL;DR: In this article, the tensile strength and impact strength along with the joint-operating cost of laser-welded butt joints made of AISI304 were investigated and the optimal welding conditions were identified in order to increase the productivity and minimize the total operating cost.
Abstract: Recently, laser welding of austenitic stainless steel has received great attention in industry. This is due to its widespread application in petroleum refinement stations, power plants, the pharmaceutical industry and also in households. Therefore, mechanical properties should be controlled to obtain good welded joints. The welding process should be optimized by the proper mathematical models. In this research, the tensile strength and impact strength along with the joint-operating cost of laser-welded butt joints made of AISI304 was investigated. Design-expert software was used to establish the design matrix and to analyze the experimental data. The relationships between the laser-welding parameters (laser power, welding speed and focal point position) and the three responses (tensile strength, impact strength and joint-operating cost) were established. Also, the optimization capabilities in design-expert software were used to optimize the welding process. The developed mathematical models were tested for adequacy using analysis of variance and other adequacy measures. In this investigation, the optimal welding conditions were identified in order to increase the productivity and minimize the total operating cost. Overlay graphs were plotted by superimposing the contours for the various response surfaces. The process parameters effect was determined and the optimal welding combinations were tabulated.
TL;DR: In this paper, the results of macrographic analysis and micro-hardness testing indicated that sound joints can be obtained in the parameters range of rotational speed equal to 800-1500rpm and welding speed of 150-400mm/min, while axial force and tool geometry were kept constant.
TL;DR: In this paper, the low hardness zones (LHZs), determined by constructing the hardness distribution maps around the heat-affected zones, changed the location and inclination with the welding conditions, but the hardness values of the LHZs were mainly dependent on the welding speed.
Abstract: Six-millimeter-thick 6061Al-T651 plates were friction stir welded with varied welding parameters and tool dimensions. The low hardness zones (LHZs), determined by constructing the hardness distribution maps around the heat-affected zones, changed the location and inclination with the welding conditions, but the hardness values of the LHZs were mainly dependent on the welding speed. The thermal cycles experienced by the LHZs had approximately the same peak temperature of 360 °C to 370 °C with varied durations that were governed by the welding speed. The microstructure of the LHZs was characterized by a low density of β′ precipitates, which tended to reduce with increasing the welding speed. The fracture of the welds occurred along the LHZs, and the tensile strength of the welds increased with increasing the welding speed and was independent of the tool dimension and the rotation rate. A heat source zone-isothermal dissolution layer model was proposed to explain the observed effects.
TL;DR: In this article, a very first attempt has been made to simulate the ultrasonic welding of metals by taking into account both of these effects (surface and volume) and a phenomenological material model has been proposed which incorporates these two effects (i.e. surface and volume).
TL;DR: In this paper, the impact of tool parameters on forces during welding, on the tool torque and tool temperature were investigated using a systematic tool profile matrix which considered the influence of four variations of each of these six geometric factors.